Education and business leaders as well as the public at large have grown increasingly concerned about the achievement disparities that children from at-risk backgrounds manifest at a young age. 1-3 Research has noted that children from low-income families, black and Hispanic children, children from Spanish-speaking homes, and children of mothers with low levels of education on average perform worse on indicators of academic achievement than their more advantaged peers. 1-6 However, much of the research and policy attention has focused on the preschool years (ages 3-5) leading immediately into the transition to kindergarten, 4, 5, 7 or on later elementary school and high school. 8 Research that has explored disparities based on sociodemographic risk factors i at earlier ages has indicated that disparities in cognitive development are evident at 24 months of age 9-11 , with a few studies documenting developmental disparities based on sociodemographic risk within the first year of life. 6, 12-14 Very little research, however, has used nationally representative data to explore whether disparities are found within the first year of life, and whether disparities are evident across a wider range of developmental outcomes. ii Early childhood initiatives that take into account the entire preschool period of 0 to 5 years need a better understanding of the disparities which may be emerging at the very youngest ages in order to address these gaps with effective, targeted interventions for children ages 0 to 3 or the full age range from birth to school entry. This brief adds to the body of knowledge by using data from a nationally-representative sample of infants born in the year 2001 to examine multiple sociodemographic characteristics that may be associated with developmental disparities at 9 and 24 months of age. We examine developmental outcomes in three domains: cognitive development, general health, and socialemotional development. First, we examine possible disparities in each of these developmental domains associated with family income, comparing infants/toddlers from families at or below 200 percent of the federal poverty threshold to those whose families are above this threshold. iii We next assess the prevalence of developmental disparities by race/ethnicity, home language, and mother's educational attainment. Although low socioeconomic status (SES) has been found to account for most of the variance in cognitive scores in previous research, 3 low SES is highly correlated with other demographic characteristics, such as racial/ethnic minority status. 15 Furthermore, previous research has shown the presence of multiple risk factors has significant effects on children's developmental outcomes. 16 In order to further explore the influence of low income and other sociodemographic factors, we examine the overlap in these characteristics i Typical sociodemographic risk factors include low family income, low parental education, single parenthood, and teen parenthood. ii As a notable example of analyses of children's abiliti...